1. Field of the Invention
This invention relates to improvements in a process of producing chlorofluoroacetones, particularly 3,3-dichloro-1,1,1-trifluoroacetone and 1,1,3,3-tetrachloro-1-fluoroacetone, which are useful as intermediate materials of medicines and agricultural chemicals and as reagents for introducing fluorine-containing groups.
2. Description of the Prior Art
A variety of processes of producing chlorofluoroacetones have been hitherto proposed and put into practical use. For example, an English translation (pages 241 to 245) of Doklady Akademii Nauk SSSR, Vol. 307, No. 6, pages 1385 to 1390, August 1989 discloses that 3,3-dichloro-1,1,1-trifluoroacetone is synthesized from 3,3,3-trichloro-1,1,1-trifluoropropane-2-one in an anhydrous solvent, through an Al-enolate intermediate, by using a mercury compound as a catalyst. Additionally, Japanese Patent Provisional Publication No. 10-287609 discloses that pentachloroacetone is fluorinated by hydrogen fluoride in a liquid phase in the presence of an antimony pentachloride thereby to form 3,3-dichloro-1,1,1-trifluoroacetone. Further, Japanese Patent Provisional Publication No. 11-1451 discloses that pentachloroacetone is fluorinated in a gas phase in the presence of a fluorination catalyst thereby to form 3,3-dichloro-1,1,1-trifluoroacetone.
The technique disclosed in the English translation of Doklady Akademii Nauk SSSR not only requires to maintain a production process strictly in an anhydrous condition but also uses mercury, which is problematic in case of employing the technique in an industrial scale. The technique disclosed in Japanese Patent Provisional Publication No. 10-287609 uses the antimony pentachloride catalyst and therefore provides corrosion of a reactor, which is problematic as an industrial process. Further, by the technique disclosed in Japanese Patent Provisional Publication No. 11-1451, a relatively large amount of reduction products such as 3-chloro- 1,1,1 -trifluoroacetone and 1,1,1 -trifluoroacetone is produced.